086ic Maxim/Dallas > App Notes > AUTOMOTIVE BATTERY MANAGEMENT GENERAL ENGINEERING TOPICS POWER-SUPPLY CIRCUITS PROTOTYPING AND PC BOARD LAYOUT Keywords: EMI, EMC, voltage regulator, LDO, switching regulator, step-down, buck, step-up, boost, flyback, SEPIC, common-mode, Faraday shield, core geometries, leakage inductance, crosstalk, ESR, ESL Nov 29, 2000 APPLICATION NOTE 716 Proper Layout and Component Selection Controls EMI Understanding the physics of voltage regulator topologies is important in designing power systems for EMI and EMC compliance. In particular, the physical principles behind switching regulators (buck, boost, flyback, and SEPIC topologies) guide component choice, magnetics design and PC board layout. Parasitic elements such as leakage inductance, ESR, and ESL are significant when optimizing circuit performance. Most portable devices include a regulator or other form of power supply, and the lower supply voltages associated with smaller-lithography ICs have mandated these power circuits in many nonportable devices as well. Though not fully understood by many designers, the trade-off among different types of regulators and power supplies can have a major effect on battery life, compliance with electromagnetic interference/ electromagnetic compatibility (EMI/EMC) regulations, and even the basic operation of a product under design. The following overview covers the mechanisms and the physical principles governing the generation and the propagation of e